title: Effects of elevated CO2 and nitrogen deposition on ecosystem carbon fluxes on the Sanjiang plain wetland in Northeast China.
abstract: BACKGROUND
  Increasing atmospheric CO2 and nitrogen (N) deposition across the globe may affect ecosystem CO2 exchanges and ecosystem carbon cycles. Additionally, it remains unknown how increased N deposition and N addition will alter the effects of elevated CO2 on wetland ecosystem carbon fluxes.
  
  
  RESULTS
  Beginning in 2010, a paired, nested manipulative experimental design was used in a temperate wetland of northeastern China. The primary factor was elevated CO2, accomplished using Open Top Chambers, and N supplied as NH4NO3 was the secondary factor. Gross primary productivity (GPP) was higher than ecosystem respiration (ER), leading to net carbon uptake (measured by net ecosystem CO2 exchange, or NEE) in all four treatments over the growing season. However, their magnitude had interannual variations, which coincided with air temperature in the early growing season, with the soil temperature and with the vegetation cover. Elevated CO2 significantly enhanced GPP and ER but overall reduced NEE because the stimulation caused by the elevated CO2 had a greater impact on ER than on GPP. The addition of N stimulated ecosystem C fluxes in both years and ameliorated the negative impact of elevated CO2 on NEE.
  
  
  CONCLUSIONS
  In this ecosystem, future elevated CO2 may favor carbon sequestration when coupled with increasing nitrogen deposition.
authors.affiliation: Key Laboratory for Vegetation Ecology, Ministry of Education, Institute of Grassland Science, Northeast Normal University, Changchun, Jilin Province, PR China.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Wang
authors.forename: Tingcheng
authors.initials: T
authors.lastname: Zhu
authors.forename: Hongwei
authors.initials: H
authors.lastname: Ni
authors.forename: Haixiu
authors.initials: H
authors.lastname: Zhong
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Fu
authors.forename: Jifeng
authors.initials: J
authors.lastname: Wang
mesh_terms: D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D057486:Carbon Cycle; D002245:Carbon Dioxide / Q000378:metabolism*; D002681:China; D017753:Ecosystem; D005843:Geography; D019684:Magnoliopsida / Q000254:growth & development / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D011891:Rain; D012621:Seasons; D012987:Soil / Q000737:chemistry; D013696:Temperature; D053833:Wetlands
chemical_list: D009566:Nitrates; D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon; D009584:Nitrogen; C006568:ammonium nitrate